The present invention is directed to a gas blast switch.
The invention refers to a gas blast switch of the type described in FIG. 1 of the U.S. Pat. No. 4,139,752. In the known switch, extinguishing gas heated by the switching arc is stored in a toroidal shaped hot space coaxially surrounding the contacts and radially blasts the switching arc when the heating effect of the switching arc decreases as the current to be interrupted approaches a crossover. In order to obtain a blasting of the switching arc which is as effective as possible, a cooling device is provided in the annular duct. The temperature of the extinguishing gas used to blast the switching arc is reduced by the cooling device when passing through the annular duct. A cooling device is, however, relatively expensive and makes the flow of the extinguishing gas more difficult, both into the hot space during the high current phase and out of the hot space when the current to be interrupted approaches a crossover.
The invention, as characterised in the claims, satisfies the objective of providing a gas blast switch of the generic type but in which the extinguishing gas provided for blasting the switching arc is, even without the use of a cooling device, available at gas temperatures quite substantially below the temperature of the heated extinguishing gas.
The gas blast switch in accordance with the invention is characterised by high extinguishing capability and simple construction. This is due to the fact that the extinguishing gas heated by the switching procedure generates, in the hot space, a circulation flow by means of which the heated extinguishing gas and the cool extinguishing gas located in the hot space are very rapidly mixed.